Author's note: these pages were written some years ago. I am not planning to update them. For a more current coverage, see the Palaeos website (to which many links on these pages point to anyway. More info here

Cynognathidae

A large and powerful preditor, and dominant animal for many millions of years, Cynognathus was one of the largest cynodonts. The head was proportionally very large (upto 30 to 45 cm in length) and somewhat doglike in appearance, hence the name Cynognathus ("dog jaw"). The skull is rather narrow, with a short temporal region, which served for the attachment of very powerful muscles for closing the jaws. Practically the whole of the lower jaw on each side was made up of a single bone, the dentary, into which were set the teeth the cutting incisors, stabbing canines and shearing cheek teeth. Behind the small, peglike incisors was a gap, followed by the large canine. A great bony flange (the coronoid process) at the back of the dentary articulated with the skull, and enabled the jaws to be opened wide. This flange also provided a large area to which extra jaw muscles could attach, giving the jaws tremendous bite-power.

The body also was strongly built, with its hindlimbs placed directly beneath its body. The knee pointed forward and the elbow backward, giving an erect mammalian posture. Clearly this was an efficient preditor, perfectly adapted to its environment, which persisted with little or no change for some five or ten million years. review of the cynodonts gives only a single species, but it is possible that there were several very similiar species, possibly in different parts of Pangea, and perhaps suceeding each other as the Triassic period progressed.

Although a very succesful animal, Cynognathus died out during the middle Triassic period, to be replaced by the smaller carnivorous Chiniquodontids and the small to large herbivorous Traversodontids. It is likely that the very arid conditions of the Triassic worked against the mammal-like Cynognathus and in favour of the reptilian archosaurs (the Thecodonts) which had become the unchallanged masters of the land by the middle Triassic.

FAMILY CYNOGNATHIDAE Watson 1917

Horizon:early Triassic period: Cynognathus Zone of South Africa and Lesotho; Puesto Viejo Formation of Argentina; China.
Age:Spathian to AnisianDistribution: Only known so far from Gondwana, although it is not unlikely that these animals had a worldwide ( Pangea) distribution, perhaps limited by local geographic or environmental factors.
preferred food: other tetrapods
length: about one and a half meters long
weight: the size of a large wolf - adults 50 to 70 kg
Metabolism: partially or completely endothermic
Potential Predators: large Erythosuchid thecodonts
Ancestor:GalesauridaeReplaced:GalesauridaeReplaced by:ChiniquodontidaeDescendents:Chiniquodontidae and DiademodontidaeTaxonomic status - monogeneric Family

Remarks:Generic and specific distinctions within the Cynognathidae have been based on characters which vary with age (tooth number and morphology, skull proportions) and are influenced by postmortem deformation. Karoomys, Cistecynodon, and Nythosaurus browni are based on tiny juveniles of Cynognathus. In their review of the Cynodontia Hopson and Kitching recognize only a single species, pending a thorough revision of the family.

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page by M.Alan Kazlevpage uploaded 6 September 2000. Reposted and last modified 1 September 2005, links updated 16 January 2010